Some distillers estimate that the yeast contributes about 25 percent of the whiskey's flavor, so it's highly significant. What makes one yeast better than another I can't say. A distiller is looking for a yeast that is robust in its propagation action and, of course, one that makes the whiskey taste good.

There used to be a big distinction made between practical distillers and scientific distillers, with the former catching wild yeast from the environment and the latter using pure strain yeast, bred in a laboratory. Today that is somewhat blurred.

Yeast is a microorganism and there are an unlimited number of different strains. They are as unique as humans or, perhaps more accurately, human families. I'll resist drawing the analogy to the specific biological process, but the product of that process varies in subtle ways depending on the metabolism of the yeast family at work in a particular plant, hence the fermented mash and, ultimately, the whiskey has a distinctive taste.

To taste yeast characteristics you want to taste younger whiskeys. That is where the tastes from the yeast and grains are more pronounced, because there is less taste coming from the wood.

Four Roses uses five different yeast strains making its whiskey. As I understand it, they distill separate batches of each of the yeasts and two different mashbills, resulting in ten different whiskeys which they combine to get their preferred flavor profile. The current Bulleit bourbon is a Four Roses product but using a single yeast and single mashbill.

1. I know that most (all?) bourbons are cold filtered before they are bottled to avoid a cloudiness at cool temperatures, how is this achieved? Are the pipes run through a cooling tank? Or is the vat refrigerated?

2. GTS and Bookers are both uncut, unfiltered. Does this include cold filtering as well? Are there any other bourbons unfiltered and/ or barrel proof?

3. How many actual filtration processes are there between mash and bottle?

1. I know that most (all?) bourbons are cold filtered before they are bottled to avoid a cloudiness at cool temperatures, how is this achieved? Are the pipes run through a cooling tank? Or is the vat refrigerated?

2. GTS and Bookers are both uncut, unfiltered. Does this include cold filtering as well? Are there any other bourbons unfiltered and/ or barrel proof?

3. How many actual filtration processes are there between mash and bottle?

Contrary to popular belief...there are lots of filters before product gets to the bottle...They only way for a product to be absolutely NON-FILTERED is...to pour it straight from the barrel to the bottle...

There are filters in the dump room to filter out the large chunks of charcoal...

There are filter's on the tank for the first holding...so it will not clog...the entrance and the exit...

There are filter's in the filler so that it can enter (we call them socks) and exit (looks like fishnet) for a free flow...

Chill filtration is cooling the product to -17 degrees...I don't know what the other distilleries low point chill is...

Another factor is adding carbon...if they are not chilling they are adding carbon to prevent flock---I am not saying everyone adds carbon...but "other's" add carbon ...

This is so interesting...I find it amazing that some folks say they "taste" the difference. I really want to see if they can

I am adding a new element to our "Bourbonian Taster of the Year" contest...Truman, (etohchem) has generously offered samples of chilled and unchill filtered bourbon for the tasting...

Here is a link to a great pdf file, (careful, it's a big 'un) published as a textbook for a college level microdistilling class.http://http://www.distillery-yeast.com/ARTISANDISTILLING1.0.0.pdfWhich has great info on everything from the amount of alcohol to expect from a mash, to heat transfer and chemical equations for an idealized still.
It is geared mainly towards brandy, vodka, and fuel ethanol, but there is lots of good info in there on grain alcohol too.

So, I took a couple of weeks worth of vacation before a LOOONNGGG deployment I have coming up, and I got bored and started pondering one of my favorite subjects: bourbon. Here is what I came up with: I plan on movong to Kentucky before I am 23, I would love to play around with a small still in a barn on my own property, I figure I would have upwards of 60 years to play around and get it right, I think this would be awesome.

Now, aside from all the logistics involving mashbills, water, stills, barrels, aging, filtering and bottling, what kind of legalities are involved? I of course realize that "moonshining" is illegal, but what if I wanted a legal "micro-distillery"? Is it even possible? Does the FDA and the ATF get involved? I see tons of micro-breweries, why not homemade bourbon? What do you all think?